This invention relates generally to heat exchangers placed within gas turbine engines. More particularly, the present invention relates to a heat exchanger having an internal passageway and being disposed within the fluid flow path prior to the combustor. Although the present invention was developed for use in a gas turbine engine, certain applications may be outside of this field.
In gas turbine engines, cooling air is generally bled off at various stages within the compressor and used for cooling elsewhere in the engine. As pressures and temperatures increase within gas turbine compressors, the temperature of the cooling air increases to a point where its usefulness as a cooling agent becomes minimal. Heat exchangers located outside the flow path of the gas turbine engine require complex piping and, therefore, introduce additional weight as well as pressure loses inefficiencies. Some studies placing heat exchangers within gas turbine engines have been undertaken and show promising results.
In FIG. 1 there is illustrated a prior art configuration of an internal heat exchanger. The cooling fluid enters heat exchanger 10 through inlet manifold 12, flows through thin-walled tubing 13, and exits heat exchanger 10 through outlet manifold 14. Airflow 16 passes over cooling tubes 13 and the cooling fluid within tubes 13 absorbs heat from airflow 16. The design of such prior art heat exchangers is costly due to the intensive assembly that requires multiple braze joints 18 to attach cooling tubes 13 to manifolds 12 and 14.
The invention described herein provides cooling means for reducing the cooling air bled off from the compressor of a gas turbine engine.
One form of the present invention contemplates a heat exchanger having an internal passageway and being disposed within the fluid flow path prior to the combustor so that the cooling air from the compressor is cooled as it flows over the outer surface of the heat exchanger.
In another embodiment of the invention, the heat exchanger is of an integral cast configuration and has a serpentine internal passageway. Eliminating the need for multiple-braze joint reduces the cost of such a cast heat exchanger.
The cooling medium flowing within the internal passageway of the heat exchanger can be fuel which cools the compressed air that is generally bled off from the compressor. The vaporized fuel is then supplied to the combustor of the gas turbine engine.
Furthermore, a series of heat exchanger segments can be arranged axially, thereby eliminating the need for separate individual heat exchangers of varying lengths.
One object of the present invention is to provide a unique heat exchanger.
Related objects and advantages of the present invention will be apparent from the following description.